In a typical water heater, cold or ambient temperature water is introduced into the bottom of the water heater tank, where it is detected by a sensor that triggers a call for heat. When a water heater is subjected to repeated short draws of hot water in which the water draw stops shortly after a call for heat is initiated, the water temperature in the tank can stratify and lead to water at the top of the water heater being much hotter than the desired temperature setting. This phenomenon is also referred to as stacking.
Stacking can be reduced by implementing a relatively large temperature differential setting, such as 20° Fahrenheit (F). That is, with a differential of 20° F., the water temperature as measured by the sensor must drop 20° below a water temperature set-point before a call for heat is initiated. However, over a few hours of inactivity, the water in the tank will cool and any hot water draws made before a call for heat is initiated may result in complaints that the water is too cold.
For example, where a hot water heater is set to 120° F., and the differential is set to 20° F., water in the tank may cool to 101° F. overnight such that any draw of hot water in the morning may be too cold. Thus, large differential settings may result in cold water complaints if the no hot water draws are made over an extended period of time. On the other hand, a narrower differential setting decreases energy efficiency and may cause stacking, as the water heater turns on more often as the water temperature drops over time. Thus, there is a need for control of a water heater that reduces stacking effects yet maintains a comfortable hot water temperature.
This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.